How do I create a contact horizon for use in layered models?
To construct the model including a contact, you will need to construct a version of the contact horizon that is bound by the neighbouring horizons.
Refer to this diagram:
![](https://media.screensteps.com/image_assets/assets/003/312/009/original/7400c4a8-ebd8-4099-be85-42ee13db74e2.png)
- In Map View, open the Operations tab and select Horizon Math.
- Add the two bounding horizons ("top" - Top Res, "base" - Base Res).
- Set the property of each to TVD (assumes you have a velocity model configured for Time-Depth conversion).
- Use this formula to create a constrained constant surface (e.g. at 2500):
if (top > 2500, top, if (base < 2500, base, 2500)) - Set the output Z dimension to TVD.
- Click Run.
Rename the result to something useful, e.g. constrainedOWC.
Replace the constant value in your model with this constrained horizon.